Good list. It's not likely SocSec is going to be eliminated but smaller cost of living increases, and the like, or even smaller total benefits, are possible. Not many things I could add to your list..maybe one:

In addition to healthcare, another large expense may be transportation. So if they plan to spend 20,000 every 10 years, on a replacement car, they need to add $2,000 per year or almost $200/month. (adjust these numbers depending on how much they plan to spend and how often they plan to replace) and adjust for inflation.

More generally, the budget should include not only what one spends in a typical year but those rare every-many-years but expensive purchases. Appliances and home repairs are two others that come to mind if they own rather than rent.

Also are they living on same budget as they plan to in retirement? If not, do a test run before they retire to make sure they can really stick to that budget. And, do they plan to retire somewhere else? Research cost of living there, carefully. Again, very solid list this is just a few possible augments to.